ABB Relion 670 Series Applications Manual page 314

Section 20
Remote communication
Important to know when connecting LDCM to SMAI function block with 3 or 8 ms cycle time.
Link forwarding
If it is not possible to have a communication link between each station, the solution has been to
set the protection up in a slave-master-slave configuration. This means that in Figure 116, only IED-
B has access to all currents and, therefore, this is the only place where the differential current is
evaluated. If the evaluation results in a trip, the trip signal will be sent over the two communication
links.
IEC16000077 V1 EN-US
Figure 116: Three-end differential protection with two communication links
If the LDCM is in 2Mbit mode, you can send the three local currents as well as the three remote
currents from the other links by configuring the transmitters in IED-B:
1. Ldcm312 transmitter sends the local currents and the three currents received by Ldcm313.
2. Ldcm313 transmitter sends the three local currents and the three currents received from
Ldcm312.
As a result, six currents are received in IED-A and IED-C. These currents can be connected to the
protection function together with the local three currents.
This setup results in a master-master-master configuration, but without the benefit of reverting
to a slave-master-slave configuration in case of a communication link interruption. In case of a
communication link interruption, all three IEDs would be blocked.
20.1.2.1 Communication hardware solutions
The LDCM (Line Data Communication Module) has an optical connection such that two IEDs can be
connected over a direct fiber (multimode), as shown in figure 117. The protocol used is IEEE/ANSI
C37.94. The distance with this solution is typical 110 km/68 miles.
308
Doing so will affect all protections for the connected cycle time.
LDCM 64kbit will increase trip time about 5 - 15 ms during normal conditions.
LDCM 2Mbit will increase trip time about 2-3 ms during normal conditions.
In addition IED can get transmission delay from communication either from direct
fiber or other equipment such as MUXs etc. Maximum supported communication
delay is 40 ms.
3-end differential protection with two communication links
Ldcm312
IED-A
Ldcm312
In order to forward the logic signals (for example, inter-trip or inter-block) between
IED-A and IED-C, the setting
LDCM313 for Ldcm312 and to LDCM312 for ldcm313.
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Ldcm312
IED-B
Ldcm313
LinkForwarded should be defined. In IED-B, it is set to
1MRK 511 407-UUS Rev. J
GUID-DD3CF47C-A202-4416-954A-EFC0F8BEBCB7 v1
IED-C
IEC16000077-1-en.vsd
Phasor measurement unit RES670
Application manual
M12844-11 v7